Riboswitches: Regulators of modern and ancient metabolism

Advances in nucleic acid biochemistry continue to reinforce the hypothesis that RNA has enormous potential for forming complex shapes. Some structured RNAs are known to function as highly specific receptors and others as efficient enzymes. These examples prove that some of the basic needs of primitive life forms could have been satisfied by RNA alone. Recent findings suggest that RNAs also can work as molecular sensors and switches that control biological processes in modern cells. This article provides an overview of the function of metabolite-sensing ‘riboswitches’ and explores the possibility that such molecules were used by primitive organisms to regulate complex biochemical pathways.